An ultrasonic non-destructive testing (NDT) probe is placed on the surface of a titanium alloy component. The speed of the ultrasonic wave in the titanium alloy is 6000 m s-1.
The probe emits a short pulse and detects a reflected echo from a subsurface defect located at a depth of 18 cm, as shown in the diagram:
How long is the time delay between the emission of the pulse and the detection of the reflected echo?
3.0×10−5 s3.0 \times 10^{-5}\text{ s}3.0×10−5 s
6.0×10−5 s6.0 \times 10^{-5}\text{ s}6.0×10−5 s
3.0×10−3 s3.0 \times 10^{-3}\text{ s}3.0×10−3 s
6.0×10−3 s6.0 \times 10^{-3}\text{ s}6.0×10−3 s